The referenced publication "Motronic--Kombiniertes ZUnd- und Benzineinspritzsystem" ("Motronic--Combined Ignition and Fuel Injection System"), published by the assignee of the present application, January 1983--describes a control apparatus for motor vehicles which includes an arrangement sensing acceleration of the engine and, upon determining that the engine accelerates, controlling the ignition instant--with respect to a reference position--such as top dead center (TDC) of a piston by changing the ignition advance angle and, further, providing for additional fuel to the fuel-air mixture.
If the throttle is opened abruptly, with the speed of the engine remaining constant, the air-fuel mixture will become leaner for a short period of time. In order to obtain good transition for smooth engine operation, with higher throttle opening, it is necessary to increase the fuel component of the fuel-air mixture. The control unit recognizes presence of acceleration, from the difference of the load signal which suddenly appears with respect to a prior signal, and, in such a case, increases the fuel component by enriching the fuel for acceleration. The air-fuel mixture may be controlled to a ratio of lambda=0.9, to obtain maximum torque. This prevents hesitation of the engine during acceleration.
The foregoing sequence occurs while the engine is warm. During the warm-up phase of the engine, however, the normal enrichment of the fuel for acceleration is insufficient. If the engine is cold, the enrichment must be increased due to the poor intermixing between fuel and air and possible condensation of liquid fuel on the intake manifold and/or the intake runner tubes. A temperature-dependent enrichment factor can be provided which is controlled, with respect to time, approximately linearly. The rate of change is independent of absolute temperature of the engine.
The control unit is capable of matching the ignition advance angle based on input information parameters of loading and speed at all times, by computing the proper ignition angle, in the interval between two ignition events. If a predetermined change in loading is exceeded, the control unit senses this excess and adds a fixed ignition angle, typically retardation angle, which, after first being added, is controlled with respect to the duration of its presence. This operation prevents knocking or pinging of the engine, which might, otherwise, occur for a few operating cycles or strokes of the engine if the ignition timing would be controlled only in accordance with its ordinary retardation function, and which, otherwise, might occur upon intense acceleration in some engines. Additionally, the high nitrogen-oxygen compounds in the exhaust gas which occur upon acceleration are reduced.
In those cases in which sudden and abrupt change of the ignition timing instant for the internal combustion engine (ICE) is commanded, a jolt or jerk may be sensed by the occupant of the vehicle. It is possible to avoid pinging of the engine, however, in those instances in which abrupt change is absolutely necessary, for example upon transition from partial loading. The control unit permits such fast change.